1. Field of the Invention
The present invention relates to a method of producing optical film laminates. More particularly, the present invention relates to a method of producing optical film laminates that each include three or more optical films, such as a polarizing film and an optical compensation film, which are laminated to each other.
2. Description of the Related Art
In recent years, not only polarizing films but also various kinds of optical film, such as retardation films and brightness enhancement films are frequently used in the form of a laminate of three or more layers thereof for a liquid crystal display device. Even for an image display device other than a liquid crystal display device, plural optical films are sometimes used in the form of a laminate of three or more layers thereof.
An optical film laminate having three or more layers of such optical films laminated together are produced by forming three or more optical films, such as polarizing film and an optical compensation film independently of each other, bonding them together and cutting a laminate intermediate into a predetermined size and a predetermined shape. One of characteristic features of an optical film laminate lies in that each optical film has an optical orientation axis. When this optical film laminate is formed, the respective layers must be laminated to each other to allow the optical orientation axis of each optical film to define a predetermined angle.
Hitherto, investigation has been carried out on a method of producing optical film laminates by laminating three or more layers of optical films, as shown in FIG. 5. Specifically, the method includes cutting out rectangular film pieces 111, 112, 113 from first to third optical film webs 101, 102, 103 respectively at predetermined angles, bonding these rectangular film pieces 111, 112, 113 together, cutting a thus obtained laminate intermediate 104 into small pieces having a predetermined shape (e.g., rectangular shape) to provide product chips 105. This method will be also hereinafter referred as a single plate bonding method.
According to the single plate bonding method, product chips 105 can be produced from substantially the entire area of the laminate intermediate 104 having the film pieces 111, 112, 113 laminated together, provided that these film pieces cut out from the first to third optical film webs have a uniform shape. Thus, the single plate bonding method is advantageous in that even three or more layer of optical films can be laminated to each other by remarkably simple steps.